Prime Cuts: Slicing Open Four Types of Shock Absorbers

We kill some dampers for your edification.

Shock absorbers (a.k.a. suspension dampers) are the unsung heroes of ride and handling. Lacking them, your car would porpoise over bumps and flounder on its springs through bends. As their name suggests, these tubular oil-filled devices damp (slow down) wheel and body motion, resulting in a comfortable ride, predictable steering response, and agile maneuverability. A piston fitted with tiny orifices is stroked through oil contained within a sealed tube, creating the resistance that restrains wheel and body motion. But why do some dampers work so well while others don’t? Searching for answers, we ran a band saw through four examples to get a look inside.

KYB Excel-G

This twin-tube unit is the most common and least-expensive type of damper. In addition to the piston orifices used to restrict oil flow during compression (wheel moving up) and rebound (wheel moving down), a foot valve [A] (not visible) regulates flow between the inner and outer tubes. This flow is necessary because the rod displaces some oil as it enters the inner tube. A bag filled with nitrogen gas applies constant pressure to the oil, thereby resisting the formation of bubbles.

Tenneco Continuously Controlled Electronic Suspension System

This triple-tube damper has a computer-controlled valve [B] to regulate oil flow from the innermost tube through a second concentric tube and, finally, into an outer reservoir. A broad range of damping and an infinite number of settings are available in both compression and rebound. Numerous Audi, Ford, Mercedes-Benz, and Volkswagen models use versions of this electronically adjustable damper.

KYB Gas-a-Just

All valving is located on the piston [C] in this single-tube damper. Gas contained at high pressure in a separate sealed chamber [D] allows the rod to enter the tube without displacing any oil. The high gas pressure improves damping efficiency and consistency, which is why this design is common in performance applications.

BWI MagneRide

Electric coils inside this single-tube dampers piston [E] create a local magnetic field. Iron particles suspended in the oil align with that field to restrict flow through the pistons orifices. Switching the electric current on and off provides rapid changes in the amount of damping provided. This design is the best at providing minimal damping for a gentle ride, ultra-firm damping for excellent handling, and speedy transitions between those two extremes.